In the Right Pane, right click on "Security Zones and Content Ratings" and select "Properties"
3.
Modify Security Zones Properties

At the properties Window, Select the "Import the current security zones and privacy settings" radio button and click "Modify Settings"*

*Note... the first time you attempt this, it may ask you to confirm your intension of only modifying those clients who are not running IE under the special "Enhanced Security Configuration" (usually reserved for server instances). This How-To only covers modifying the "Trusted Sites" for standard IE installations.

From the "Internet Properties" window, select the "Trusted Sites" category and click the "Sites" button.

4.
Enter your Trusted Sites to the List

List your desired "Trusted" sites to the list, making note of the potential requirement of a secure (https) URL near the bottom.

5.
Link your GPO to the Appropriate OU

Subject says it all - Now that you've created your Group Policy Opject, link it to the appropriate Organizational Unit to ensure it will be applied to the users who need the trusted sites added.